This invention relates to calcining systems provided with a planetary cooler, and more particularly it is concerned with a calcining system of the type described which is capable of effecting adjustments of the flow rate of a cooling fluid flowing through the cooler.
In a calcining system, such as a system for calcining cements, a planetary cooler provided with air extracting means is known for use with a rotary kiln for cooling clinker which comprises a plurality of cooling cylinders arranged parallel to the center axis of the rotary kiln and spaced apart equidistantly therefrom for movement around an orbit. Clinker in the cooling cylinders is cooled by cooling air which exchanges heat with the clinker and is heated, and a portion of the heated cooling air is led to the rotary kiln and the rest is extracted and led to other place, such as a calciner, as preheating air.
In a calcining system provided with this type of cooler, coating might fall in the rotary kiln and the operating condition might change, with a result that the clinker delivered to the planetary cooler might show variations in volume. The cooling air exhausted from the planetary cooler is supplied to a kiln or a calciner as air for combustion. It has hitherto been usual practice to keep the flow rate of the cooling air constant to stabilize the condition of combustion. Thus when the clinker is introduced in large volume into the planetary cooler, the clinker would not be cooled satisfactorily and clinker of high temperature would be discharged from the system. When the clinker discharged from the planetary cooler is not cooled satisfactorily, various troubles would ensue. The clinker of high temperature might give damage to the transporter or might reduce the quality of the clinker. The efficiency of the grinder might reduce. If cooling air is supplied to the planetary cooler in a quantity which is more than is necessary for the aforesaid combustion to effect cooling of the clinker satisfactorily, the temperature at which calcining of the clinker is effected would drop and the quality of the clinker would be reduced. In the prior art, proposals have been made to increase the length of the cooling cylinders of the planetary cooler, to apply a spray of water to the clinker or blowing a cooling stream of air against the clinker and to mount an additional cooler posterior to the planetary cooler, to obtain sufficient cooling of the clinker. However, these measures increase the cost and are bad economy.